Process for producing structure, structure thereof, and magnetic recording medium

ABSTRACT

The present invention relates to a process for producing a structure having holes at prescribed positions. The structure is produced through steps of (A) providing an impressing member having protrusions, and a substrate, (B) forming a layer, on the substrate, from a material having a less strength than the impressing member, (C) forming depressions by impressing the impressing member on the layer corresponding to protrusions of the impressing member, (D) etching the layer to bare at least a part of the surface of the substrate, and (E) anodizing the substrate to form holes on the substrate.

TECHNICAL FIELD

The present invention relates to a process for producing a structurehaving holes, particularly to a process for producing a functionalstructure like a magnetic recording medium having holes filled with afunctional material like a magnetic material.

BACKGROUND ART

A new technique, nano-imprinting, is disclosed 15 for forming ananometer-sized structure on a surface of an article by impressingdirectly a structure having protrusions on a working object, beingdifferent from conventional lithography utilizing a light beam or anelectron beam (U.S. Pat. No. 5,772,905).

In this technique, as shown in FIGS. 9A to 9D, stamper 100 having aprotrusion pattern 103 of a size of tens or hundreds of nanometersformed by an electron beam or the like is impressed on thin resin 25film 104 formed on flat substrate 105 and then detaching the stampertherefrom to form a projection-depression pattern: depression portion(molded region) 106 of the resin film is removed by reactive ion etchingor a like method; and substrate 105 is etched by utilizing the unremovedremaining resin layer 107 as the mask to form structure 107, 108 havingnano-metric projection-depressions corresponding to the originalstamper. In this method, to prevent the deterioration of the stamper byimpression operation, the impressing action is stopped before top face141 of protrusion 103 of stamper 100 comes into direct contact withsubstrate 105 carrying thin resin film 104, and the stamper is detached.In this method, even if the impressing action is stopped before theprotrusion top face of the stamper comes into direct contact with thesubstrate, the resin of the thin film can rise by the impression to comeinto contact with bottom face 142 of the depression portion of thestamper.

This contact may make irregular the formed protrusion-depressionstructure of the thin resin film on detaching of the stamper from thethin resin film.

The present invention intends to provide a structure having holes atdesired positions.

DISCLOSURE OF THE INVENTION

According to an aspect of the present invention, there is provided aprocess for producing a structure having holes, comprising steps of (A)providing an impressing member having protrusions, and a substrate, (B)forming a layer, on the substrate, from a material having a lessstrength than the impressing member, (C) forming depressions byimpressing the impressing member on the layer corresponding toprotrusions of the impressing member, (D) etching the layer to bare atleast a part of the surface of the substrate, and (E) anodizing thesubstrate to form holes on the substrate.

According to another aspect of the present invention, there is provideda process for producing a functional structure comprising a step offilling a functional material into the holes formed in the process.

In a structure of the present invention, the term “protrusion” and“protruded portion” means a portion protruded from the surround, i.e.depression defined in the following. The term “depression” and“depressed portion” means a portion comprised of a bottom having a levellower than that of a top of the adjacent protrusion. The term“protrusion-depression structure” means a structure consisting of theprotrusion and the depression. When directing the attention to a patternof protrusions of the protrusion-depression structure, the structure maybe called as “protrusions structure”, and when doing of depression, itmay be as “depression structure”. Patterns of these structures arecalled as “protrusion-depression structure pattern” or“protrusion-depression pattern” for short; “protrusion structurepattern” or “structure pattern” for short; and “depression structurepattern” or “depression pattern” for short, respectively. The distancebetween the top of a protrusion and the bottom of the adjacentdepression is the “height of the protrusion” or the “depth of thedepression”.

The process for producing a structure of the present invention comprisesthe steps of forming a pattern by impressing an impressing member havinga protrusin-depression structure consisting of plural protrusions anddepressions on a patterning layer on a workable layer, and detaching theimpressing member from the patterning layer. In this process, the topfaces of the protrusions of the protrusion structure (hereinafterreferred to as “protrusion top faces”) has a size not larger than 500 nmand a height of not larger than 10 μm, the patterning layer is madethinner than the height of the protrusions of the impressing member toprevent the contact of the surface of the patterning layer with thedepressed bottom of the protrusion-depression structure of theimpressing member.

The above-mentioned size of the top face of the protrusion of theimpressing member means a diameter for a circle-shaped face, and anoutside diameter for polygon-shaped face. The height of the protrusionis in the range from several nanometers to 10 μm, preferably from tensof nanometers to 5 μm.

In a preferred process for producing a nano-structure of the presentinvention, patterning layer is formed on a workable layer in a thicknessless than the height of the protrusion of the stamper, and the stamperis impressed on the opposing patterning layer to form in the patterninglayer a depression pattern corresponding to the protrusion pattern ofthe stamper.

The patterning layer thinner than the height of the protrusions of thestamper reduces the adverse effects of air bubbles, renderingunnecessary a vacuum atmosphere. After the impressing operation, theworkable layer is bared by etching, and bared portion is worked byanodization or like a treatment. Thus a simple nano-printing method isprovided which does not require strict position control in theimpressing direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C are sectional views for explaining Example 1 of thepresent invention.

FIGS. 2A, 2B, and 2C are sectional views for explaining Examples 2 and 3of the present invention.

FIGS. 3A and 3B are sectional views for explaining Examples 2 and 3 ofthe present invention.

FIGS. 4A, 4B, and 4C are sectional views for explaining Example 4 of thepresent invention.

FIGS. 5A and 5B are surface views for explaining an example ofarrangement of the depressed structure of the present invention.

FIGS. 6A, 6B, and 6C are sectional views for explaining Example 5 of thepresent invention.

FIGS. 7A, 7B, and 7C are sectional views for explaining Example 6 of thepresent invention.

FIGS. 8A, 8B, and 8C are sectional views for explaining Example 7 of thepresent invention.

FIGS. 9A, 9B, 9C, and 9D are sectional views for explaining an exampleof prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention are described below.

In a preferred embodiment of the present invention as shown in FIGS. 4Ato 4C, a stamper (impressing member) having a protrusion pattern formedthereon is placed in opposition to a workable layer having a patterninglayer provided thereon, and the stamper is impressed on the patterninglayer such that at least the tops of the protrusions are brought asclose as about 50 nm or less to the workable layer surface and isdetached to form the protrusion pattern on the patterning layer,corresponding to the stamper.

In the case where the patterning layer is formed from a material whichbecomes less viscous in proportion to temperature elevation, preferablythe stamper is impressed on the patterning layer heated to obtainsuitable viscosity, and after cooling, the stamper is detached.

The nano-structure prepared as shown in FIGS. 2A and 2B is preferablydry-etched or wet-etched to bare the workable layer at the depressedportions of the patterning layer, and the nano-structure obtained aboveis preferably anodized to form a depression structure in the workablelayer as shown in FIG. 2C.

In the step of baring the workable layer, the dry-etching or wet-etchingis conducted preferably to bare the workable layer at the depressedportions of the patterning layer and to form depressions (holes) ofdepth of 1 nm or more in the workable layer (FIG. 2B).

The stamper has preferably at least one pair of protrusion-depressionstructures at intervals of not more than 1 μm between the protrusions.

The patterning layer is formed preferably from a flowable thin-coatingmaterial such as a resin solution in a solvent, a resin materialcontaining an alkoxide or a silicone, and silsesquioxane.

The workable layer is composed preferably of a metal containingaluminum.

The workable layer is constituted preferably of an underlayer composedof a metal other than aluminum and a surface layer containing aluminum.

In a process of producing the nano-structure of the present invention,preferably as shown in FIGS. 1A to 1C, stamper 1 having a pattern ofprotrusions 4 is placed in opposition to workable layer 3 havingpatterning layer 2 of a thickness smaller than the height of protrusions4 of the protrusion-depression structure; stamper 1 is impressed tobring the tops of protrusions 4 as close as 50 nm or less to the surfaceof workable layer 3; and the stamper is detached therefrom to form aprotrusion pattern corresponding to stamper 1 on patterning layer 2.

Stamper 1 having at least one protrusion or depression is formed bylithography employing an electron beam, an X-ray, ultraviolet light,visible light, or the like, wet-etching or dry-etching, electron beamdirect-writing, anodic oxidation, and the like technique. The surface ofprotrusion 4 is preferably flat: plural protrusions have preferably thetop faces placed on one and the same plane. The protrusion structure haspreferably an arrangement of columns in a triangular lattice state asshown in FIG. 5A, or may have a multiple periodic arrangementconstituted of several regular constitutions as shown in FIG. 5B. In theFIG. 5B, an arrow denoted by numeral 15 indicates a triangular latticeregion, an arrow denoted by numeral 16 indicates a rectangular latticeregion, and an arrow denoted by numeral 17 indicates a graphite latticeregion. Dots 18 on boundary lines between the regions belong to both theregions.

In the production process of the present invention, preferably as shownin FIGS. 1A to 1C, patterning layer 2 is formed by applying a liquidmaterial on workable layer 3 by spin coating or a like method: theliquid material being mainly composed of a flowable thin-coatingmaterial such as a resin solution in a solvent, a resin materialcontaining an alkoxide or a silicone, and silsesquioxane. The thicknessof patterning layer 2 is made smaller than the height of protrusion 4 ofstamper 1. Then, stamper 1 is placed in opposition to patterning layer2; the stamper is impressed to bring the tops of protrusions 4 as closeas 50 nm or less to the surface of workable layer 3; and the stamper isdetached therefrom to form a depression pattern corresponding toprotrusion pattern 4 in stamper 1 on patterning layer 2. The impressingmember is preferably a regularly arranged protrusion structure having asurface layer composed of silicon, nickel, or the like, and ispreferably coated with a releasing material such as a fluoro-resin, anda silane coupling agent for improving releasability.

The smaller thickness of patterning layer 2 than the height ofprotrusions 4 of the stamper reduces the adverse effect of an air bubbleimprisoned in depression portion 5 of the stamper to impede the patternformation. This makes unnecessary a vacuum atmosphere for the impressingand detaching operation. The working object 9 to be worked is preferablyheated to a temperature necessary for obtaining a lower viscosity ofpatterning layer 2 before the impression operation.

The structure produced as above is subjected preferably to dry-etchingor wet-etching to remove patterning layer 2 remaining at bottoms 70 ofdepression portions 7 of the patterning layer to bare workable layer 3(FIGS. 2A and 2B).

For example, in the case where workable layer 3 is composed of anelectroconductive material such as a metal and patterning layer 2 iscomposed of an insulating material such as a resin, electroplating canbe conducted by utilizing protrusions 6 of patterning layer 2 afterpattern formation as a mask and the bared portions of workable layer 3as an electrode. Thereafter by immersion into a solution capable ofdissolving selectively patterning layer 2, a structure can be obtainedwhich has a protrusion-depression structure corresponding to that ofstamper 1 from a different material.

In the case where workable layer 3 is made from a material mainlycomposed of aluminum, alumina nano-holes can be obtained by anodizationstarting from the bared portions of the etched workable layer obtainedby etching the remaining film at bottom 70 of depression 7 of thepatterning layer. If the patterning layer is soluble in the anodizationsolution, the layer is protected by lamination of thin protection layer11 made of a metal like aluminum (FIG. 6B) which can be dissolved duringthe anodization, and then the anodization is conducted (FIG. 6C) asshown in FIGS. 6A to 6C.

In the case where the bared portions of the workable layer are alsoetched more or less during the etching treatment as shown in FIGS. 7A to7C, the patterning layer is removed (FIG. 7B) and then the anodizationis conducted (FIG. 7C).

The anodization is conducted specifically by application of a voltage byutilizing the workable layer having the patterning layer as the anode inan acidic solution such as an aqueous oxalic acid solution and anaqueous sulfuric solution. The oxidation and dissolution by theanodization is initiated predominantly from the depression portions ofthe patterning layer to form fine holes arranged in the depressionpattern. The voltage to be applied is considered generally to be equalto the arrangement cycle multiplied by a factor of 2.5⁻¹ [V/nm]. Forexample, for a triangular lattice arrangement of 100 nm intervals, avoltage of 40 volts is applied. The average cycle length of the formedfine holes depends on the applied voltage. Accordingly, in formation ofregular triangular depression pattern on patterning layer 2 andsubsequent formation of the fine holes on bottoms 70 of depressions 7,slight disturbance of regular arrangement of the depression structurecan be corrected automatically into regular arrangement of the fineholes by action of the applied anodization voltage.

In the case where the patterning layer is made of a material which isdissolvable at a suitable dissolving rate-uniformly by the anodizationsolution, the etching process may be omitted. With start of theanodization, the patterning layer begins to dissolve to bare theworkable layer at bottoms 70 of the depressions. Then electric currentcomes to flow through the bared layer portions to form nano-holes on theworkable layer. When the patterning layer is made of a material which isnot soluble in the anodic oxidation solution, no change occurs on theworkable layer surface.

The diameter of the formed nano-holes can be enlarged as desired byimmersion in a solution capable of dissolving the workable layer, suchas an aqueous phosphoric acid solution.

Various functional structure can be produced by filling the holes with afunctional material by electrodepositing, sputtering, or a like method.In particular, a magnetic recording medium can be obtained by fillingthe fine holes with a magnetic material by electrodeposition.

EXAMPLE

The present invention is described below in detail by reference todrawings.

EXAMPLE 1

An example of the present invention is described below by reference toFIGS. 1A to 1C.

Stamper 1 having protrusion-depression pattern formed thereon isimpressed to opposing workable layer 3 having patterning layer 2 havinga thickness less than the height of protrusions 4. After the tops of theprotrusions 4 has reached the position 30 nm to the surface of workablelayer 3, the stamper is detached, thereby forming a protrusion patternof stamper 1 on patterning layer 2.

For example, columnar protrusions 4 having a diameter of 30 nm and aheight of 75 nm are formed at arrangement intervals of 100 nm on a baseplate by electron beam projection and dry-etching to prepare stamper 1.Separately, on Si substrate 8, there are formed workable layer 3composed of silicon oxide (SiO₂) in a thickness of 100 nm and patterninglayer 2 composed of polymethyl methacrylate (PMMA) in a thickness of 50nm. This PMMA layer is formed by applying a solution thereof in ethylcellosolve acetate solution by spin coating. Stamper 1 is placed inopposition to patterning layer 2, and impressed thereon at a substratetemperature of 120° C. with an impression load of 1000 kgf/cm². Afterimpression for 30 seconds and cooling to 60° C., the stamper is detached(FIGS. 1A and 1B). The height of the protrusion 6 (non-impressedportion) of patterning layer 2 is increased slightly by the flow ofresin corresponding to the volume of formed depressions 7 by theimpression, and the resin remains in a thin film state on the bottom 70of depression 7 owing to nonuniformity of the stamper. shape.

The thickness of patterning layer 2 is smaller than the height ofstamper protrusion 4. Therefore, the air bubble, which is usuallyimprisoned in depression portion 5 of the stamper and impedes thepattern formation, is allowed to escape through the depression space ofthe stamper to the outside. Therefore, the fine pattern can be formedwithout vacuum application by the impression operation. The requiredimpression pressure is less because of the smaller contact area.Further, since the height of protrusion 6 (non-impressed portion) of thepatterning layer after pattern formation depends on the initial filmthickness of patterning layer 2 and the shape of stamper 1, fineadjustment of the impression load and position control of the impressiondirection are not necessary.

EXAMPLE 2

An example of the present invention is described below by reference toFIGS. 2A to 2C and FIG. 3.

The structure having been prepared by the process for production of anano-structure in Example 1 is subjected to dry-etching or wet-etchingto remove the remaining resin material from bottoms 70 of depressions 7of the patterning layer to bare workable layer 3.

Stamper 1 described in Example 1 is placed in opposition to workingobject 9 having workable layer 3 composed of aluminum (Al) of 100 nmthick and having patterning layer 2 composed of PMMA. Stamper 1 isimpressed thereon at a substrate temperature of 120° C. at a load of1000 kgf/cm² for a holding time of 30 seconds, and after cooling to 60°C.,the stamper is detached to obtain a structure shown in FIG. 1C. Thestructure is subjected to dry-etching in an oxygen atmosphere to removethe resin remaining at bottoms 70 of depressions 7 of the patterninglayer to bare Al (FIG. 2A). Otherwise, the etching may be conducted inan atmosphere of a mixture of BCl₃ and O₂ to remove simultaneously theAl below bottom 70 of depression 7 of the patterning layer to formhollows (FIG. 2B).

Thereafter, tin-copper solder electroplating is conducted by utilizingprotrusion portion 6 of the patterning layer as the mask and workablelayer 3 as the electrode, and then protrusion 6 of the patterning layeris selectively removed by ultrasonic acetone washing to obtain asolder-protrusion structure having protrusions in an nanometericintervals.

Otherwise, lamination film 10 is formed from a desired material bysputtering or a like method as shown in FIG. 3A, and protrusion 6 of thepatterning layer is selectively removed by ultrasonic acetone washing toobtain protrusion structure shown in FIG. 3B.

EXAMPLE 3

An example of the present invention is described below by reference toFIGS. 2A to 2C and FIGS. 3A and 3B.

Stamper 1 described in Example 1 is placed in opposition to workingobject 9 having workable layer 3 composed of Al and having patterninglayer 2 composed of silsesquioxane. Stamper 1 is impressed thereon withthe substrate kept at room temperature with a load of 1200 kgf/cm² for aholding time of 30 seconds. Then the stamper is detached. The workedobject is dry-etched in an atmosphere of argon and SF₆ to bare Al (FIG.2A). The dry-etched object is subjected to anodization by utilizing theAl as the anode in an aqueous 0.3 mol/L oxalic acid solution at atemperature of 16° C. by application of a voltage of 40 V. Since theanodization is initiated at the bared portion, nanometer-sized holes areobtained which have a high aspect ratio and are arranged in a pattern ofthe patterning layer (FIG. 2C). The silsesquioxane, which is insolublein an aqueous oxalic acid solution, need not be removed.

EXAMPLE 4

An example of the present invention is described below by reference toFIGS. 4A to 4C.

Stamper 1 having a protrusion-depression pattern formed thereon isimpressed on workable layer 3 having patterning layer 2 thereon, andthen detached. Thereby, a depression pattern which is counter to theprotrusion pattern of stamper 1 is formed in patterning layer 2.

As an example, from an Si base plate, stamper 1 is prepared by formingcolumnar protrusions 4 of 30 nm diameter and 75 nm high in a triangularlattice arrangement at intervals of 100 nm by electron beam lithographyand dry-etching. The top faces of the highest protrusions 4 arepositioned preferably on one and the same plane. Separately, onsubstrate 8, there are formed workable layer 3 of 100 nm thick composedor silicon oxide (SiO₂) and patterning layer 2 of 100 nm thick composedof polymethyl methacrylate (PMMA) as shown in FIGS. 4A to 4C. The PMMAis applied as a solution in ethyl cellosolve acetate by spin coating.Stamper 1 is placed in opposition to patterning layer 2, and isimpressed thereon at a substrate temperature of 120° C. at a load of 500kgf/cm². The stamper and the substrate are cooled at that state to 60°C., and then the stamper is detached (FIGS. 4A, 4B, and 4C). The resinin a volume corresponding to the volume of depression 7 is allowed toflow, whereby the thickness around the impressed portions of patterninglayer 2 increases slightly in comparison with that before theimpression. At the bottoms 70 of depressions 7, the resin remains in athin film owing to nonuniformity of the stamper shape and incompleteflow of the resin.

An air bubble may be imprisoned in depression 5 of stamper 1 dependingon the shape of the pattern. This imprisoned air can impede the flow ofthe resin, and makes difficult the formation of the pattern in preciseaccordance with the stamper shape. This adverse effect can be reduced byraising the substrate temperature to increase the flowability of theresin, decreasing the thickness of patterning layer 2 to be less thanthat of protrusion 4, or other counter measures.

EXAMPLE 5

An example of the present invention is described below by reference toFIGS. 6A to 6C.

The structure obtained by the process of production of a nano-structurein Example 4 is subjected to dry-etching or wet-etching to remove theresin remaining on bottoms 70 of depressions 7 of the patterning layerto bare workable layer 3.

Stamper 1 described in Example 4 is placed in opposition to workingobject 9 constituted of Si substrate 8, and workable layer 3 composed ofaluminum (Al) of 200 nm thick and patterning layer 2 composed of PMMAformed on the substrate. Stamper 1 is impressed thereon at a substratetemperature of 120° C. at a load of 500 kgf/cm², and is detached aftercooling to 60° C. to obtain a structure shown in FIG. 4C. This structureis subjected to dry-etching in an oxygen atmosphere to removeselectively the resin remaining at bottoms 70 of depressions 7 of thepatterning layer to bare Al (FIG. 6A). Then as shown in FIG. 6B,protection layer 11 is formed from Al in a thickness of 5 nm bysputtering. Anodization is conducted by utilizing this layer as theanode in an aqueous oxalic solution (0.3 mol/L, 16° C.) by applicationof 40 V. Thereby alumina nano-holes are formed as shown in FIG. 6C. Thenano-holes are formed from bottoms 70 of depressions 7 of the patterninglayer in a triangular lattice arrangement at intervals of 100 nm.Protection layer 11 serves to protect patterning layer 2 from corrosionin the acidic solution, and can be removed later by ultrasonic washingin a solution capable of dissolving aluminum such as an aqueousphosphoric acid solution. The PMMA can also be removed by ultrasonicwashing in a solvent such as an aqueous phosphoric solution, andacetone.

EXAMPLE 6

An example of the present invention is described below by reference toFIGS. 7A to 7C.

In the preparation of the nano-structure described in Example 5 orExample 2, both the resin remaining at bottoms of depressions 7 of thepatterning layer and Al can be simultaneously removed by etching in anmixed etching atmosphere containing BCl₃ and O₂ to form hollows on theAl surface (FIG. 7A). Thereafter, the PMMA is removed by ultrasonicacetone washing or ozone-ashing (FIG. 7B). This working object as theanode is subjected to anodization in an aqueous oxalic acid solution(0.3 mol/L, 16° C.) by voltage application of 40 V to form aluminanano-holes as shown in FIG. 7C. The nano-holes are formed starting fromhollows 13 on the surface of the Al, and are arranged in triangularlattice at intervals of 100 nm.

EXAMPLE 7

An example of the present invention is described below by reference toFIGS. 8A to 8C.

A stamper having a protrusion-depression pattern is placed in oppositionto a workable layer having a patterning layer, and is impressed thereonand detached therefrom to form, on the patterning layer, a depressionpattern corresponding to the protrusion pattern of the stamper.

Next, on a substrate composed of Si, a titanium film is formed in athickness of 10 nm, and further thereon an aluminum film is formed in athickness of 500 nm as a workable layer. Further thereon, a patterninglayer is formed from aluminum alkoxide in a thickness of 75 nm. Thealuminum alkoxide is applied as an IPA (isopropyl alcohol) solution byspin coating. The stamper employed in Example 4 is placed in oppositionto the patterning layer, and impressed thereon at a substratetemperature of 150° C. with a load of 1000 kgf/cm². The stamper and theobject are cooled to 60° C. by keeping the impressing state. Thereafterthe stamper is detached. The patterning layer becomes slightly thickeraround the impressed points after the impression corresponding to thevolume of the flow of the resin caused by the impression. The resinremains at the bottom portions of the depression in a thin film owing tononuniformity of the stamper shape and incomplete flow of the resin.

This working object as the anode is subjected to anodic oxidation in anaqueous oxalic acid solution (0.3 mol/L, 16° C.) by application of avoltage of 40 V. In this operation, the aluminum alkoxide is graduallyhydrolyzed and dissolved in the aqueous oxalic acid solution. Therefore,the electric current begins to flow firstly at the depression bottomswhere the workable layer is bared, which initiates formation of thealumina nano-holes. The alumina nano-holes are formed by the anodizationperpendicularly to the substrate and can readily be obtained in a highaspect ratio, which cannot be attained by usual photolithography oretching.

After immersion in an aqueous phosphoric acid solution (0.3 mol/L) for40 minutes, regular alumina nano-holes are obtained which have adiameter of 30 nm and a depth of 500 nm.

Finally, a magnetic recording medium is obtained by filling the holeswith a magnetic material by electrodeposition.

The present invention provides a process for producing a nano-structureby a nano-imprinting in combination with dry-etching, wet-etching, oranodic oxidation; enabling simple production of depression typestructure.

1-9. (canceled)
 10. A process for producing a structure having holes,comprising the steps of: providing on a substrate to be anodized a firstmember having a patterning layer comprised of a material soluble atanodization; impressing a second member having protrusions on thepatterning layer to form a protrusion-depression structure at thepatterning layer; and forming holes on the substrate by anodizing thesubstrate, wherein the anodizing is conducted by allowing a portionconsisting of a material comprising the patterning layer to remain asthe depression portion of the protrusion-depression structure andstarting the anodizing from the bottom of the depression portion. 11.The process according to claim 10, wherein the patterning layer isconstituted by a material being of lower strength than a materialconstituting the second member.
 12. The process according to claim 10,wherein the patterning layer contains an alkoxide.
 13. The processaccording to claim 10, wherein the height of the protrusion portion ofthe second member is greater than the thickness of the patterning layer.14. A process for producing a functional structure, which comprises astep of filling the holes formed in the process according to claim 10with a functional material.
 15. A process for producing a magneticrecording medium, wherein the functional material in the processaccording to claim 10 is a magnetic material.